With the increasing importance attached to environmental protection, the environmental laws are becoming more and more stringent, where reducing the sulfur content of gasoline and diesel oil is deemed as one of the most important means to improve the air quality. Most of the sulfur in gasoline products comes from the thermal processed gasoline blending components, such as catalytic cracking gasoline. Therefore, the reduction of sulfur content in thermal processed gasoline is favorable to the reduction of sulfur content in gasoline products. The current gasoline product standard of China, GB 17930-2016, “Gasoline for motor vehicles”, requires the sulfur content in gasoline products to be no more than 50 μg/g. And, the quality standard for gasoline products will become more stringent in the future. Under such circumstances, catalytic cracking gasoline has to be subjected to a deep desulfurization, so as to make the gasoline product conformable to the environmental protection requirement.
Currently, there are two primary processes for the deep desulfurization of oil products, i.e., selectively catalytic hydrodesulfurization and catalytic hydrogenation adsorption desulfurization. In the catalytic hydrogenation adsorption desulfurization process, sulfides in hydrocarbon oils are removed via adsorption at a certain temperature and pressure in the presence of hydrogen. This process has the characteristics of low hydrogen consumption and low requirement on the purity of hydrogen, such that it has extensive potential applications in the desulfurization of fuel oils.
CN1355727A discloses an adsorbent composition useful for removing sulfur from cracking gasoline and diesel fuel, consisting of zinc oxide, silica, alumina and nickel, wherein the nickel is present substantially in reduced state in an amount capable of removing sulfur from the cracking gasoline or diesel fuel stream in contact with the nickel-containing adsorbent composition under desulfurization conditions. The composition is obtained by granulating a mixture of zinc oxide, silica and alumina to form particles, drying, calcinating, followed by impregnation with nickel or a nickel-containing compound, drying and calcinating again, and then reducing.
CN1382071A discloses an adsorbent composition useful for removing sulfur from cracking gasoline and diesel fuel, consisting of zinc oxide, silica, alumina and cobalt, wherein the cobalt is present substantially in reduced state in an amount capable of removing sulfur from the cracking gasoline or diesel fuel stream in contact with the cobalt-containing adsorbent composition under desulfurization conditions.
U.S. Pat. No. 6,150,300 discloses a process for preparing an adsorbent, comprising the following steps for preparing spherical particles: (a) mixing a composition comprising silica, a composition comprising a metal oxide dispersed in an aqueous media and a composition comprising zinc oxide to form a first mixture without extruding the first mixture; and (b) spheroidizing the first mixture to produce particles having diameters of 10-1000 mm. Step (a) may further comprise mixing with a metal promoter.
CN1422177A discloses an adsorbent composition useful for removing sulfur from cracking gasoline and diesel fuel, consisting of zinc oxide, expanded perlite, alumina and a metal promoter, wherein the metal promoter is present substantially in reduced state in an amount capable of removing sulfur from the cracking gasoline or diesel fuel stream in contact with the composition under desulfurization conditions.
CN1627988A discloses an adsorbent composition useful for removing elemental sulfur and sulfur compounds from cracking gasoline and diesel fuel, comprising zinc oxide, expanded perlite, aluminate and a metal promoter, wherein the metal promoter is present in an amount capable of removing sulfur from the cracking gasoline or diesel fuel stream in contact with the composition under desulfurization conditions, and at least a part of the metal promoter is present in zero valence state.
CN1856359A discloses a process for producing a composition, comprising the steps of: a) mixing a liquid, a zinc-containing compound, a silica-containing material, alumina and a co-catalyst, to form a mixture; b) drying the mixture, to form a dried mixture; c) calcinating the dried mixture, to form a calcinated mixture; d) reducing the calcinated mixture with a suitable reducing agent under appropriate conditions, to produce a composition comprising a co-catalyst content in reduced state, and e) recovering the composition. The co-catalyst comprises a plurality of metals selected from the group consisting of nickel and the like.
CN1871063A discloses a process for producing a composition, comprising the steps of: a) mixing a liquid, a zinc-containing compound, a silica-containing material, and alumina, to form a mixture; b) drying the mixture, to form a first dried mixture; c) calcinating the first dried mixture, to form a first calcinated mixture; d) incorporating a promoter into or onto the first calcinated mixture, to form a promoted mixture; e) contacting the promoted mixture with an acid selected from the group consisting of citric acid, tartaric acid and combinations thereof, to form a contacted mixture; f) drying the contacted mixture, to form a second dried mixture; g) calcinating the second dried mixture, to form a second calcinated mixture; h) reducing the second calcinated mixture under appropriate conditions using a suitable reducing agent, to produce a composition comprising a promoter content in reduced state, and i) recovering the composition.
Though the adsorbents disclosed have certain desulfurization capability, the requirement on the sulfur content of gasoline products is becoming more and more stringent as the quality standard for gasoline increases. Moreover, such kind of catalysts are susceptible to abrasion during use, which requires continuous replenishment of the catalyst, and thus increases the operation cost. It thus can be seen that new catalysts with higher desulfurization activity and abrasion resistance are still needed.